This invention relates to a filter apparatus and method of its operation, particularly to a pressure filter and method for extracting liquids from wet slurry fluids and for producing a substantially-dry filter cake of the solid materials present in such slurry fluids.
In many industrial processes and other applications where a slurry of solids and liquids is produced, it becomes necessary to filter the slurry solids from the liquids so that these materials may be efficiently utilized or, alternatively, disposed in an environmentally-safe manner. To separate the solids from the liquids, a filter apparatus, such as a pressure filter, is often used. Known pressure filters generally include one or more pairs of filter plates capable of relative motion. The plate inlet is adapted for receiving the slurry while the filtered liquids, called the filtrate, are collected by means of the plate outlet which also provides the requisite support for a filter medium positioned between the filter plates. This arrangement permits a filtration chamber to be defined by the inlet plate and the filter medium when the plates are pressed together. In the usual production cycle of such a filter, slurry is introduced into the filtration chamber under pressure through one or more inlet port, whereby the slurry distributes itself throughout the chamber. After the filtration chamber is filled with slurry, the filter executes a series of programmed operations, namely, washing and/or treating the contents of the chamber in a particular manner, as well as pressurizing the chamber to force the liquids from the slurry through the filter medium, leaving the slurry solids, consolidated in a substantially-dry filter cake, within the chamber. The chamber is then opened, allowing the dry filter cake to be removed therefrom.
In the filter apparatus of the type here discussed, the filter is operated in a batch mode; i.e. apparatus open, apparatus closed, slurry input, treatment of the slurry to develop a cake, apparatus opened, filter medium moved as cake is discharged and advanced to the next cycle position, and then repeating the above steps. The present invention relates to improvements and modifications of pressure filter apparatus. Some of the improvements are intended to adapt such filters for “food grade” or “pharmaceutical grade” applications, and some of the modifications are to accomplish convenience in operation in such filters as well as to improved performance.